Polymer particles

ABSTRACT

Biodegradable, cross-linked polymer particle embolics and methods of making the same are described. The particle embolics can be used as embolization agents.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/719,241, filed Sep. 28, 2017, which claims the benefit of U.S.provisional patent application No. 62/401,091, filed Sep. 28, 2016, andU.S. provisional patent application No. 62/428,990, filed Dec. 1, 2016,the entire disclosures of which are incorporated herein by reference.

FIELD

Biodegradable polymer particles for the occlusion of vascular sites andcavities within the body, such as the embolization of tumors orarteriovenous malformations, are described.

SUMMARY

Described herein generally are biodegradable, cross-linked polymerparticles. In some embodiments, the particles can have a spherical shapeor be substantially spherical. Thus, the particles described herein canbe referred to as microspheres or polymer spheres. These polymers can beused for/in embolization. The polymer particles can include and/or beformed of one or more monomers and a crosslinker susceptible to chemicalhydrolysis or enzymatic action.

The biodegradable polymer particles described herein can be utilized forthe occlusion of vascular sites, bodily lumen, and other cavities withinthe body. In some embodiments, the polymer particles can be used forsuch purposes as the embolization of tumors or arteriovenousmalformations.

Polymer particles can comprise: at least one monomer and at least onecrosslinker. In some embodiments, the polymer particles can besusceptible to degradation through chemical hydrolysis or enzymaticaction. Particles as described herein can have various sizes dependingon a particular use, but generally can have diameters between about 40μm and about 1,200 μm or between about 75 μm and about 1,200 μm.

Methods of making a polymer particle as described herein are alsodescribed. These methods comprise: preparing a prepolymer solutionincluding at least one monomer, at least one crosslinker susceptible todegradation through chemical hydrolysis or enzymatic action, and aninitiator; dispersing the prepolymer solution in mineral oil; andforming the polymer particles via polymerization of the monomers.

Other methods to form polymer particles can include: reacting aprepolymer solution in an oil to form the polymer particles. Theprepolymer solution can include at least one monomer comprising at leastone functional group, at least one crosslinker susceptible todegradation through chemical hydrolysis or enzymatic action, and aninitiator.

In one embodiment, the polymer particles can be prepared from monomershaving a single functional group suitable to polymerization. Functionalgroups suitable to free radical polymerization, include but are notlimited to, acrylate, acrylamide, methacrylate, and methacrylamide.Other polymerization methods including nucleophile/N-hydroxysuccinimideesters, nucleophile/halide, vinyl sulfone/acrylate ormaleimide/acrylate, can be utilized. Selection of the monomers can begoverned by the desired mechanical properties of the resulting particleand minimizing the biological effect of the degradation products.

In some embodiments, the monomer used can include an ionizablefunctional group that is basic (e.g. amines, derivatives thereof, orcombinations thereof). A basic, amine group may be protonated at pH'sless than the pKa of the amine, and deprotonated at pH's greater thanthe pKa of the amine. In other embodiments, the monomer can include anionizable functional group that is acidic (e.g. carboxylic acids,sulfonic acids, phosphoric acids, derivatives thereof, or combinationsthereof). The acid group may be deprotonated at pH's greater than thepKa of the acid, and protonated at pH's less than the pKa of the acid.

In one embodiment, the at least one crosslinker can include at least twofunctional groups suitable to polymerization and at least one linkagesusceptible to breakage and/or cleavage. This breakage and/or cleavagecan impart biodegradation to the polymer particle. Linkages susceptibleto breakage in a physiological environment include those susceptible tohydrolysis, including esters, thioesters, carbamates, anhydrides,phosphoesters, peptides and carbonates. Multiple crosslinkers could beutilized to control the rate of degradation in a manner that is notpossible with only one.

DRAWINGS

FIG. 1 illustrates grading scores for the samples included in Example10. (5) no change in particle numbers, outlines, or quantity from thebeginning of the experiment, (3) faint particle outline with a goodnumber of particles still visible, (1) very few particles visible, and(0) no particles observed in the sample. Results for the comparison ofdifferent crosslinking agents are illustrated in FIG. 1. The resultsillustrate that degradation rate can be dependent on the structure ofthe crosslinker used.

FIG. 2 illustrates graphically, particle degradation time at 37° C. as afunction of two different types of monomers with the same crosslinkerand concentration.

FIG. 3 illustrates graphically, particle degradation time at 37° C. as afunction of the amount of crosslinker.

FIG. 4 illustrates high performance liquid chromatography results fromExample 11.

FIGS. 5 and 6 illustrate systemic concentration of pharmaceutical agentelution in plasma overtime.

DETAILED DESCRIPTION

Described herein generally are particles made of polymer material. Thepolymer material can be a reaction product of one or more monomers andone or more crosslinkers. The monomers can include a singular functionalgroup amenable to polymerization. In some embodiments, the polymerparticles can be susceptible to hydrolysis or enzymatic action. Theparticles can be referred to herein as being microparticles,microspheres and the like. The particles can have a diameter of betweenabout 40 μm and about 1,200 μm or between about 75 μm and about 1,200μm. The particles can also be compressible and/or durable for ease ofdelivery through a medical device such as a needle or catheter. Theparticles can also be biodegradable once delivered.

The particles can be formed from a mixture such as a prepolymersolution. The prepolymer solution can comprise: (i) one or more monomersthat contain a singular functional group amenable to polymerization and(ii) one or more crosslinkers. In some embodiments, a polymerizationinitiator may be utilized.

In some embodiments, if one of the monomer(s) and/or crosslinker(s) is asolid, a solvent can be utilized in the preparation of the particles foruse as embolics. If liquid monomers and crosslinkers are utilized, asolvent may not be required, but may still be desired. In someembodiments, even when using liquid monomers and crosslinkers, a solventmay still be used. Solvents may include any liquid that can dissolve orsubstantially dissolve a monomer, monomer mixture, and/or a crosslinker.Any aqueous or organic solvent may be used that dissolves the desiredmonomer(s), crosslinker(s), and/or polymerization initiators. In oneembodiment, the solvent can be water. In another embodiment, the solventcan be N,N-dimethylformamide, formamide, or dimethyl sulfoxide. In oneembodiment, if an organic solvent is used, dimethyl sulfoxide may beused for dispersion. In other embodiments, if an organic solvent isused, an aqueous media may be used for dispersion. Additionally,solutes, e.g. sodium chloride, may be added to the solvent to increasethe rate of polymerization. Solvent concentrations can be about 10% w/w,about 20% w/w, about 30% w/w, about 40% w/w, about 50% w/w, about 60%w/w, about 70% w/w, about 80% w/w, about 90% w/w, between about 20% w/wand about 80% w/w, between about 50% w/w and about 80% w/w, or betweenabout 30% w/w and about 60% w/w of the solution.

Any type of crosslinking chemistry can be utilized to prepare thedescribed polymer particles. In some embodiments, for examplecrosslinking chemistries such as, but not limited tonucleophile/N-hydroxysuccinimide esters, nucleophile/halide, vinylsulfone/acrylate or maleimide/acrylate, or free radical polymerizationcan be used. In one example embodiment, free radical polymerization canbe used. As such, monomers with a singular ethylenically unsaturatedgroup, such as acrylate, acrylamide, methacrylate, methacrylamide, andvinyl, may be used when employing free radical polymerization.

Any amount of monomer can be used that allows for a desired particle.Monomer concentration in the solvent can be about 1% w/w, about 2% w/w,about 3% w/w, about 4% w/w, about 5% w/w, about 10% w/w, about 15% w/w,about 20% w/w, about 30% w/w, about 40% w/w, about 50% w/w, about 60%w/w, about 70% w/w, about 80% w/w, about 90% w/w, about 100% w/w,between about 1% w/w and about 100% w/w, between about 40% w/w and about60% w/w, between about 50% w/w and about 60% w/w, between about 10% w/wand about 50% w/w, between about 20% w/w and about 60% w/w, or betweenabout 40% w/w and about 60% w/w.

Monomers can be selected based on imparting desired chemical and/ormechanical properties to the polymer particle or particle embolic. Ifdesired, uncharged, reactive moieties can be introduced into theparticle embolic. For example, hydroxyl groups can be introduced intothe particle embolic with the addition of 2-hydroxyethyl acrylate,2-hydroxymethacrylate, glycerol monomethacrylate, derivatives thereof,or combinations thereof. Alternatively, uncharged, relatively unreactivemoieties can be introduced into the particle embolic. For example,acrylamide, methacrylamide, methyl methacrylate, dimethyl acrylamide,derivatives thereof, or combinations thereof can be added.

In some embodiments, the monomers can be glycerol monomethacrylate anddimethylacrylamide. The concentration of glycerol monomethacrylate inthe solvent can be about 1% w/w, about 2% w/w, about 3% w/w, about 4%w/w, about 5% w/w, about 10% w/w, about 15% w/w, about 20% w/w, about30% w/w, about 40% w/w, about 50% w/w, about 60% w/w, about 70% w/w,about 80% w/w, about 90% w/w, about 100% w/w, between about 1% w/w andabout 100% w/w, between about 5% w/w and about 50% w/w, between about10% w/w and about 30% w/w, between about 15% w/w and about 25.

The concentration of dimethylacrylamide in the solvent can be about 1%w/w, about 2% w/w, about 3% w/w, about 4% w/w, about 5% w/w, about 10%w/w, about 15% w/w, about 20% w/w, about 30% w/w, about 40% w/w, about50% w/w, about 60% w/w, about 70% w/w, about 80% w/w, about 90% w/w,about 100% w/w, between about 1% w/w and about 100% w/w, between about1% w/w and about 10% w/w, between about 1% w/w and about 5% w/w, betweenabout 5% w/w and about 10% w/w.

In one embodiment, polymer particles can be prepared from monomershaving a single functional group suitable for polymerization. Functionalgroups can include those suitable to free radical polymerization, suchas acrylate, acrylamide, methacrylate, and methacrylamide. Otherpolymerization schemes can include, but are not limited to,nucleophile/N-hydroxysuccinimide esters, nucleophile/halide, vinylsulfone/acrylate or maleimide/acrylate. Selection of the monomers isgoverned by the desired mechanical properties of the resulting particleand minimizing the biological effects of degradation products.

In some embodiments, the monomer can additionally contain an ionizablefunctional group that is basic (e.g. amines, derivatives thereof, orcombinations thereof). The amine group may be protonated at pH's lessthan the pKa of the amine, and deprotonated at pH's greater than the pKaof the amine. In other embodiments, the monomer additionally contains anionizable functional group that is acidic (e.g. carboxylic acids,sulfonic acids, phosphoric acids, derivatives thereof, or combinationsthereof). The acid group may be deprotonated at pH's greater than thepKa of the acid, and protonated at pH's less than the pKa of the acid.

If the binding of positively charged drugs is desired, monomers withnegatively charged moieties, e.g. carboxylic acids, or other acidicmoieties can be polymerized into the particle embolic. Acidic,ionizable, ethylenically unsaturated monomers can include, but are notlimited to, acrylic acid, methacrylic acid, 3-sulfopropyl acrylate,3-sulfopropyl methacrylate, derivatives thereof, combinations thereof,and salts thereof. On the other hand, if the binding of negativelycharged drugs is desired, monomers with positively charged moieties,e.g. amines, or other basic moieties can be included in the particle.Basic, ionizable, ethylenically unsaturated monomers can include, butare not limited to, 2-aminoethyl methacrylate, 3-aminopropylmethacrylate, derivatives thereof, combinations thereof, and saltsthereof.

In some embodiments, the negatively charged monomers can be3-sulfopropyl acrylate, potassium salt and 3-sulfopropyl acrylate. Theconcentration of 3-sulfopropyl acrylate, potassium salt and3-sulfopropyl acrylate in the solvent can be about 1% w/w, about 2% w/w,about 3% w/w, about 4% w/w, about 5% w/w, about 10% w/w, about 15% w/w,about 20% w/w, about 30% w/w, about 40% w/w, about 50% w/w, about 60%w/w, about 70% w/w, about 80% w/w, about 90% w/w, about 100% w/w,between about 1% w/w and about 100% w/w, between about 10% w/w and about50% w/w, between about 20% w/w and about 40% w/w, between about 30% w/wand about 40% w/w.

An additional factor in monomer selection can be the desire fordegradation products of the particle embolic to elicit a negligibleresponse from the host. In other embodiments, there can be desire fordegradation products of the particles to elicit substantially noresponse from the host.

A crosslinker can include two or more polymerizable groups, can joinmonomer chains together, and permit the formation of solid particles.Biodegradation can be imparted to the particle embolic by utilizing acrosslinker with linkages susceptible to degradation in a physiologicalenvironment. Over time in vivo, linkages can break and the polymerchains may no longer be bound together. The judicious selection ofmonomers can permit the formation of water-soluble degradation productsthat diffuse away and are cleared by the host. Linkages susceptible tohydrolysis, such as esters, thioester, carbamates, anhydrides,phosphoesters, peptides, and carbonates can be used in biodegradableproducts.

In one embodiment, the one or more crosslinker can include at least twofunctional groups suitable to polymerization and at least one linkagesusceptible to breakage and/or cleavage. This breakage and/or cleavagecan impart biodegradation to the polymer particle. Linkages susceptibleto breakage in a physiological environment include those susceptible tohydrolysis, including esters, thioesters, carbamates, anhydrides,phosphoesters, peptides and carbonates. Multiple crosslinkers could beutilized to control the rate of degradation in a manner that is notpossible with only one.

In other embodiments, the polymers can include a second crosslinkerincluding a second linkage selected from an ester, a thioester, acarbonate, a carbamate, a peptide cleavable by matrixmetalloproteinases, a peptide cleavable by matrix collagenases, apeptide cleavable by matrix elastases, and a peptide cleavable by matrixcathepsins.

In still other embodiments, the polymers can include a third, fourth,fifth or more crosslinkers each including the same or a differentlinkage.

Concentrations of the crosslinkers in the solvent can be about 5% w/w,about 10% w/w, about 15% w/w, about 20% w/w, about 25% w/w, about 30%w/w, about 35% w/w, between about 20% w/w and about 30% w/w, betweenabout 10% w/w and about 60% w/w, or between about 20% w/w and about 50%w/w. A skilled artisan understands how to calculate final concentrationsbased on the amount in solvent already discussed.

In other embodiments, concentrations of the crosslinkers in the solventcan be about 0.05% w/w, about 0.1% w/w, about 0.5% w/w, about 1.0% w/w,about 2.0% w/w, about 3.0% w/w, about 4.0% w/w, between about 0.1% w/wand about 4.0% w/w, between about 0.5% w/w and about 2% w/w, or betweenabout 1% w/w and about 1.5% w/w. A skilled artisan understands how tocalculate final concentrations based on the amount in solvent alreadydiscussed.

In one embodiment, crosslinkers can have a structure

wherein m is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15and/or n is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,or 18. In one embodiment, m is 1 and n is 3.

In one embodiment, crosslinkers can have a structure

wherein p is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. Inone embodiment, p is 4. In another embodiment, p is 1.

In one embodiment, crosslinkers can have a structure

wherein q is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15and/or r is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. Inone embodiment, q is 0 and r is 0.

In one embodiment, crosslinkers can have a structure

wherein s is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. Inone embodiment, s is 2.

In one embodiment, crosslinkers can have a structure

wherein t is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15and/or u is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. Inone embodiment, t is 0 and u is 0.

In one embodiment, crosslinkers can have a structure

wherein v is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. Inone embodiment, v is 5. In another embodiment, v is 1.

In one embodiment, crosslinkers can have a structure

wherein w is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. Inone embodiment, w is 5.

In one embodiment, crosslinkers can have a structure

In some embodiments, a crosslinker can be a tetra ester, a tetra-thiolester or a dithiol ester. In other embodiments, the crosslinker can be acarbonate crosslinker. A glycidyl based crosslinker may be bis-glycidylamino alcohol.

The prepolymer solution can be polymerized by reduction-oxidation,radiation, heat, or any other method known in the art. Radiationcross-linking of the prepolymer solution can be achieved withultraviolet light or visible light with suitable initiators or ionizingradiation (e.g. electron beam or gamma ray) without initiators.Cross-linking can be achieved by application of heat, either byconventionally heating the solution using a heat source such as aheating well, or by application of infrared light to the prepolymersolution. The free radical polymerization of the monomers) andcrosslinker(s) can require an initiator to start the reaction. In oneembodiment, the cross-linking method utilizes azobisisobutyronitrile(AIBN) or another water soluble AIBN derivative(2,2′-azobis(2-methylpropionamidine) dihydrochloride). Othercross-linking agents can include N,N,N′,N′-tetramethyethylenediamine,ammonium persulfate, benzoyl peroxides, and combinations thereof,including azobisisobutyronitriles. In one embodiment, the initiator isAIBN at a concentration of about 1% w/w to about 5% w/w.

Polymer particles can be produced or formed by methods including:reacting a prepolymer solution including at least one monomer includingat least one functional group, at least one crosslinker susceptible todegradation, and an initiator in an oil.

The prepolymer solution can be prepared by dissolving the monomer(s),crosslinker(s), and optionally initiator(s) in the solvent. The particleembolics can be prepared by emulsion polymerization. A non-solvent forthe monomer solution, typically mineral oil, is sonicated to remove anyentrapped oxygen. The mineral oil and a surfactant are added to thereaction vessel. An overhead stirrer is placed in the reaction vessel.The reaction vessel is then sealed, degassed under vacuum, and spargedwith an inert gas such as argon.

In another embodiment, the particles are prepared by emulsionpolymerization by dissolving the monomer(s), crosslinker(s), andinitiator(s) in the solvent. A non-solvent for the monomer solution,typically mineral oil when the monomer solvent is N,N-dimethylformamide,formamide, or dimethyl sulfoxide, is added to the reaction vessel with asurfactant. An overhead stirrer is placed in the reaction vessel. Thereaction vessel is then sealed and sparged with argon while mixing toremove any entrapped oxygen. The monomer solution is added to thereaction vessel, where stirring suspends droplets of the polymerizationsolution in the mineral oil. The polymerization is allowed to proceedovernight at room temperature.

The rate of stirring can affect particle size, with faster stirringproducing smaller particles. Stirring rates can be about 100 rpm, about200 rpm, about 300 rpm, about 400 rpm, about 500 rpm, about 600 rpm,about 700 rpm, about 800 rpm, about 900 rpm, about 1,000 rpm, about1,100 rpm, about 1,200 rpm, about 1,300 rpm, between about 200 rpm andabout 1,200 rpm, between about 400 rpm and about 1,000 rpm, at leastabout 100 rpm, at least about 200 rpm, at most about 1,300 rpm, or atmost about 1,200 rpm to produce particles with desired diameters.

The polymer particles described herein can have a generally orsubstantially spherical shape. The substantially spherical or sphericalparticles can have diameters of about 10 μm, about 20 μm, about 30 μm,about 40 μm, about 50 μm, about 60 μm, about 75 μm, about 100 μm, about200 μm, about 300 μm, about 400 μm, about 500 μm, about 600 μm, about700 μm, about 800 μm, about 900 μm, about 1,000 μm, about 1,100 μm,about 1,200 μm, about 1,300 μm, about 1,400 μm, about 1,500 μm, about1,600 μm, between about 50 μm and about 1,500 μm, between about 100 μmand about 1,000 μm, between about 75 μm and about 1,200 μm, at leastabout 50 μm, at least about 80 μm, at most about 1,500 μm, or at mostabout 1,200 μm. In some embodiments, the diameter can be between about40 μm and about 1,200 μm, between about 40 μm and about 60 μm, betweenabout 10 μm and about 50 μm, or between about 75 μm and about 1,200 μm.

The polymer particles can retain their diameters even after injectionthrough a catheter or other delivery device. In other words, the polymerparticles may not fall apart or otherwise fracture during delivery. Insome embodiments, the polymer particles can retain about 99%, about 98%,about 97%, about 96%, about 95%, about 90%, greater than about 99%,greater than about 98%, greater than about 97%, greater than about 96%,greater than about 95%, greater than about 90%, between about 90% andabout 100% of their diameter after delivery.

The polymer particles can also have a characteristic circularity or havea relative shape that is substantially circular. This characteristicdescribes or defines the form of a region on the basis of itscircularity. Polymer particles as described herein can have a fractionof circularity of about 0.8, 0.9, 0.95, 0.96, 0.97, 0.98, 0.99, greaterthan about 0.8, greater than about 0.9, or greater than about 0.95. Inone embodiment, the circularity of the polymer particles is greater thanabout 0.9.

The polymer particles can retain their circularity even after injectionthrough a catheter or other delivery device. In some embodiments, thepolymer particles can retain about 99%, about 98%, about 97%, about 96%,about 95%, about 90%, greater than about 99%, greater than about 98%,greater than about 97%, greater than about 96%, greater than about 95%,greater than about 90%, between about 90% and about 100% of theircircularity after delivery.

Polymerization can be allowed to proceed as long as necessary to produceparticles with desired resiliency. Polymerization can be allowed toproceed for about 1 hr, 2 hr, 3 hr, 4 hr, 5 hr, 6 hr, 7 hr, 8 hr, 9 hr,10 hr, 11 hr, 12 hr, 18 hr, 24 hr, 48 hr, 72 hr, 96 hr, between about 1hr and about 12 hr, between about 1 hr and about 6 hr, between about 4hr and about 12 hr, between about 6 hr and about 24 hr, between about 1hr and about 96 hr, between about 12 hr and about 72 hr, or at leastabout 6 hours.

Polymerization can be run at a temperature to produce particles withdesired resiliency and/or reaction time. Polymerization can be run at atemperature of about 10° C., about 20° C., about 30° C., about 40° C.,about 50° C., about 60° C., about 70° C., about 80° C., about 90° C.,about 100° C., between about 10° C. and about 100° C., between about 10°C. and about 30° C., at least about 20° C., at most about 100° C., or atabout room temperature. In one embodiment, polymerization occurs at roomtemperature.

After the polymerization is complete, the polymer particles are washedto remove any solute, mineral oil, unreacted monomer(s), and/or unboundoligomers. Any solvent may be utilized, but care should be taken ifaqueous solutions are used to wash particles with linkages susceptibleto hydrolysis. Washing solutions can include, but are not limited toacetone, alcohols, water and a surfactant, water, saline, bufferedsaline, and saline and a surfactant.

Optionally, the washed polymer particles can then be dyed to permitvisualization before injection into a microcatheter. A dye bath can bemade by dissolving sodium carbonate and the desired dye in water.Particle embolics are added to the dye bath and stirred. After the dyingprocess, any unbound dye is removed through washing. After dying andwashing, the particles can be packaged into vials or syringes, andsterilized.

After the preparation of the particle embolics, they can be optionallydyed to permit visualization during preparation by the physician. Any ofthe dyes from the family of reactive dyes which bond covalently to theparticle embolics can be used. Dyes can include, but are not limited to,reactive blue 21, reactive orange 78, reactive yellow 15, reactive blueNo. 19, reactive blue No. 4, C.I. reactive red 11, C.I. reactive yellow86, C.I. reactive blue 163, C.I. reactive red 180, C.I. reactive black5, C.I. reactive orange 78, C.I. reactive yellow 15, reactive blue No.19, C.I. reactive blue 21, any of the color additives that are approvedfor use by the FDA part 73, subpart D, or any dye that will irreversiblybond to the polymer matrix of the particle embolic.

If the herein described polymer particle or microsphere does notadequately bind any of the reactive dyes described above, a monomercontaining an amine can be added to the monomer solution in an amount toachieve the desired coloration. Examples of suitable amine containingmonomers include aminopropyl methacrylate, aminoethyl methacrylate,aminopropyl acrylate, aminoethyl acrylate, derivatives thereof,combinations thereof, and salts thereof. Concentrations of the aminecontaining monomers in the final product can be less than or equal toabout 1% w/w.

In another embodiment, monofunctional reactive dyes, such asmonochlorotriazine dyes and monovinylsulfone dyes, which contain onlyone reactive center can be irreversibly reacted to a monomer whichcontains a nucleophilic functional group to form a polymerizable dyemonomer. Monofunctional reactive dyes that can be utilized to synthesizedye monomers can include, but are not limited to, C.I. reactive orange78, C.I. reactive yellow 15, C.I., reactive blue No. 19, and/or C.I.reactive red 180. Monomers can include, but are not limited to,2-hydroxyethyl methacrylate, 2-aminoethyl methacrylate, and3-aminopropyl methacrylate. The synthesis of dye monomers is generallycarried out under alkaline conditions with elevated temperature. The dyemonomers can be separated from the unreacted monomers and dyes usingcolumn chromatography. The dye monomers can be added into the prepolymersolution in various combinations and ratios so that after polymerizationthe microspheres are colored without additional dyeing procedures.

The particles described herein can be sterilized without substantiallydegrading the polymer. After sterilization, at least about 50%, about60%, about 70%, about 80%, about 90%, about 95%, about 99%, or about100% of the polymer can remain intact. In one embodiment, thesterilization method can be autoclaving and can be utilized beforeadministration.

The final polymer particle preparation can be delivered to the site tobe embolized via a catheter, microcatheter, needle, or other similardelivery device. A radiopaque contrast agent can be thoroughly mixedwith the particle preparation in a syringe and injected through acatheter until blood flow is determined to be occluded from the site byinterventional imaging techniques.

In some embodiments, it may be desirable for the particles to degradeover time. In other words, the particles can be degradable and/orbiodegradable. In such embodiments, the particles can degrade to lessthan about 40%, about 30% about 20%, about 10%, about 5% or about 1%intact after about 2 days, 3 days, 4 days, 5 days, 6 days, 7 days, 8days, 9 days, 10 days, about 1 week, about 2 weeks, about 1 month, about2 months, about 6 months, about 9 months, about a year, about 2 years,about 5 years, or about 10 years. In one embodiment, the particles canbe substantially degraded in less than about 1 month. In anotherembodiment, the particles can be substantially degraded in less thanabout 6 months. In some embodiments, the particles can be substantiallydegraded within about one week. In other embodiments, the particles canbe substantially degraded within about six months. In some embodiments,the degradation can occur after implantation. In other embodiments, theparticles can be substantially degraded within about one week ofimplantation. In other embodiments, the particles can be substantiallydegraded within about one week of implantation.

In some embodiments, degradability can be accelerated with anappropriate and/or adequate enzyme. In some embodiments, the polymerparticles can be injected along with an enzyme that can accelerate thedegradation of the particles. In other embodiments, an enzyme can bedelivered to the site of the implanted particles at a remote time andaccelerate degradation at that time.

In some embodiments, the greater the percentage of a crosslinker in thefinal polymer particles, the longer degradation takes. Additionally, thelarger the particle diameter, the longer the degradation. Thus, theparticles with the longest degradation time are those that have thelargest concentration of crosslinker and the largest diameter. These twoproperties can be varied to tailor degradation time as needed.

The polymer particles described herein can be compressible yet durableenough not to break apart or fragment. Substantially no change incircularity or diameter of particles occurs during delivery through amicrocatheter. In other words, after delivery through a microcatheter,the polymer particles described herein remain greater than about 60%,about 70%, about 80%, about 90%, about 95%, about 99%, or about 100%intact after delivery.

Further, in some embodiments, the particles can stick to the tissueand/or remain in place through friction with the tissues. In otherembodiments, the particles can act as a plug in a vessel held in placeby the flow and pressure of the blood itself. In still otherembodiments, the particles can be cohesive enough to stick to oneanother to aid in agglomerating particles at a particular site ofaction.

Polymer particles described can be delivered through a microcatheter orother appropriate delivery device to a remote tissue or can be injectedthrough a needle to local tissues. The polymer particles can be used forocclusion of vascular sites and cavities within the body.

In some embodiments, the polymer particles can be configured forembolization of tumors (e.g., hypervascularized tumors) or arteriovenousmalformations. In some embodiments, a patient can be selected thatexhibits a hypervascularized tumor and/or an arteriovenous malformation.A microcatheter can be navigated to the location of the tumor ormalformation. Polymer particles as described herein can be injected intothat site to stabilize it thereby treating the patient's condition.

In some embodiments, the polymer particles are bare. In otherembodiments, the polymer particles can be loaded with a pharmaceuticalagent. A pharmaceutical agent can include, but is not limited to,irinotecan, doxorubicin, epirubicin, idarubicin, or a combinationthereof. The loading of the pharmaceutical agent into the polymerparticle can occur onsite or offsite. The concentration ofpharmaceutical agent can be determined by one of ordinary skill in theart. In some embodiments, the concentration of pharmaceutical agent canbe 0-10% w/w, 10% w/w-20% w/w, 20% w/w-30% w/w, 30% w/w-40% w/w, 40%w/w-50% w/w, 50% w/w-60% w/w, 60% w/w-70% w/w, 70% w/w-80% w/w, 80%w/w-90% w/w, or 90% w/w-100% w/w. In some embodiments, a 1 mLmicrosphere sample can be loaded with 37.5 mg doxorubicin eluted 24.5 mg(65%) over the first day. In other embodiments, a 1 mL microspheresample can be loaded with 50 mg irinotecan eluted over 45 mg (95%) overthe first day.

In some embodiments, the pharmaceutical drug can be about 5%, about 10%,about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about45%, about 50%, about 60%, about 65%, about 70%, about 75%, about 80%,about 85%, about 90%, about 95%, about 100%, at least about 5%, at leastabout 10%, at least about 15%, at least about 20%, at least about 25%,at least about 30%, at least about 35%, at least about 40%, at leastabout 45%, at least about 50%, at least about 60%, at least about 65%,at least about 70%, at least about 75%, at least about 80%, at leastabout 85%, at least about 90%, at least about 95%, at least about 100%,between about 0-10%, between about 5%-15%, between about 10%-20%,between about 15%-25%, between about 20%-30%, between about 25%-35%,between about 30%-40%, between about 35%-45%, between about 40%-50%,between about 45%-55%, between about 50%-60%, between about 55%-65%,between about 60%-70%, between about 65%-75%, between about 70%-80%,between about 75%-85%, between about 80%-90%, between about 85%-95%, orbetween about 90%-100% eluted over the first day. In some embodiments,this elution is after implantation.

In some embodiments, the pharmaceutical agent can have its highestsystemic concentration at about 1 hr, about 2 hrs, about 3 hrs, about 4hrs, about 5 hrs, about 6 hrs, about 7 hrs, about 8 hrs, about 9 hrs,about 10 hrs, about 11 hrs, about 12 hrs, about 13 hrs, about 14 hrs,about 15 hrs, about 16 hrs, about 17 hrs, about 18 hrs, about 19, hrs,about 20 hrs, about 21 hrs, about 22 hrs, about 23 hrs, about 24 hrs, atleast about 1 hr, at least about 2 hrs, at least about 3 hrs, at leastabout 4 hrs, at least about 5 hrs, at least about 6 hrs, at least about7 hrs, at least about 8 hrs, at least about 9 hrs, at least about 10hrs, at least about 11 hrs, at least about 12 hrs, at least about 13hrs, at least about 14 hrs, at least about 15 hrs, at least about 16hrs, at least about 17 hrs, at least about 18 hrs, at least about 19, atleast about 20 hrs, at least about 21 hrs, at least about 22 hrs, atleast about 23 hrs, at least about 24 hrs, more than about 1 hr, morethan about 2 hrs, more than about 3 hrs, more than about 4 hrs, morethan about 5 hrs, more than about 6 hrs, more than about 7 hrs, morethan about 8 hrs, more than about 9 hrs, more than about 10 hrs, morethan about 11 hrs, more than about 12 hrs, more than about 13 hrs, morethan about 14 hrs, more than about 15 hrs, more than about 16 hrs, morethan about 17 hrs, more than about 18 hrs, more than about 19, more thanabout 20 hrs, more than about 21 hrs, more than about 22 hrs, more thanabout 23 hrs, or more than about 24 hrs after delivery.

EXAMPLES Example 1 Biodegradable Crosslinker

Synthesis of 2-(methacryloxy)ethyl oxalyl monochloride, 3: An oven-dried100 mL three-neck round bottom flask was purged under argon. The flaskwas fitted with a stir bar and an addition funnel. To the flask wasadded oxalyl chloride (1, 20 g, 158 mmol) and anhydrous dichloromethane(DCM) (15 mL) sequentially. To the addition funnel was added2-hydroxyethyl methacrylate (HEMA) (2, 16 g, 123 mmol). The flask wascooled in an ice bath and HEMA was added dropwise to the reaction. Afterthe addition was finished, the reaction was left stirring in the icebath for 1 hour. The flask was pulled out of the ice bath and stirringwas continued for 1 hour. To work up, removed the DCM and oxalylchloride on a rotary evaporator. Avoid moisture from here on. Theproduct is a greenish liquid. It does not move on a silica TLC plate andhas strong UV absorption.

Synthesis of 4: An oven-dried 50 mL three-neck round bottom flask waspurged under argon. The, 2-(methacryloxy)ethyl oxalyl monochloride (3,12 g, 54.4 mmol) and anhydrous DCM (25.4 mL) were added to the reactionflask. Pyridine (5.08 g, 64.2 mmol) and 1,3-propanediol (1.88 g, 24.7mmol) were then sequentially added to the flask. To work up, began withfiltering off the white precipitate. The filtrate was then washed with5% citric acid (50 mL×2). The DCM fraction was then washed withsaturated sodium chloride (NaCl) (50 mL) and dried over sodium sulfate(Na₂SO₄). The solvent was removed under reduced pressure to give thecrude product as a thick yellowish liquid. The product was obtainedafter a flash column separation (normal phase, ethyl acetate(EtOAc)/hexanes) as a clear liquid.

Example 2 Biodegradable Crosslinker

Synthesis of 6-(methacryloylamino)hexanoic acid, 6: In a 50 mL roundbottom flask, 6-aminohexanoic acid (5, 8.45 g, 64.6 mmol) and sodiumhydroxide (2.6 g, 65 mmol) were dissolved in distilled water (13 mL).The flask was cooled in an ice bath. To this solution was addedmethacryloyl chloride (6.26 mL, 64 mmol) dropwise and then stirred fortwo hours. To work up, washed the reaction with DOM (12.5 mL). Theaqueous fraction was kept and the pH of the aqueous layer was adjustedto 2.0 with 1 M hydrochloric acid. The aqueous layer was extracted withEtOAc (30 mL×3). The organic fraction was combined and dried overNa₂SO₄. The solvent was removed under reduced pressure. The crudeproduct was crystallized with EtOAc and hexanes to give the product asclear crystals (4.65 g, 36.5%).

Synthesis of 6-[(2-methyl-1-oxo-2-propen-1-yl)amino]hexanoyl chloride,7: A three-neck round bottom flask was purged under argon. Then,6-(methacryloylamino)hexanoic acid (6, 2.5 g, 12.6 mmol) and DCM (50 mL)were added to the flask. Then, thionyl chloride (4.50 g, 37.8 mmol) wasadded dropwise to the solution with stirring. The mixture was stirredfor one hour. The solvent, thionyl chloride, and the byproduct wereremoved under reduced pressure to yield the product as a yellowishliquid.

Synthesis of N-(5-isocyanatopentyl)-2-methyl-2-propenamide, 8: A 100 mLround bottom flask fitted with a stir bar was purged under argon. Tothis flask was added sodium azide (0.774 g, 11.91 mmol), Adogen 464(0.011 mL), and distilled water (25.1 mL) sequentially. The flask wascooled in an ice bath. To this aqueous solution was added toluene (25.1mL) and 6-[(2-methyl-1-oxo-2-propen-1-yl)amino]hexanoyl chloride (7,2.47 g, 11.3 mmol) sequentially. The mixture was stirred for 45 minutesand the aqueous layer was removed thereafter. The organic fraction waswashed with distilled water (10 mL). The organic fraction was then driedover Na₂SO₄ and decolorized with charcoal. The Na₂SO₄ and charcoal wereremoved by filtration. The solvent was removed under reduced pressure toyield the product as a clear liquid (0.73 g).

Synthesis of allyl 3-(4-hydroxyphenyl)propionate, 11: To a 500 mLthree-neck round bottom flask fitted with a stir bar was added3-(4-hydroxyphenyl)propionic acid (9, 50 g, 0.3 mol) and allyl alcohol(10, 204 mL, 3 mol). To this mixture was added sulfuric acid (0.6 g, 6mmol). The reaction was stirred at 95° C. overnight. The contents werecooled to room temperature and poured over distilled water (200 mL). Theaqueous phase was extracted with dichloromethane (150 mL). The organicfraction was subsequently washed with distilled water (200 mL),saturated sodium bicarbonate (NaHCO₃) solution (200 mL, followed by 150mL), and brine (200 mL). The organic fraction was dried over magnesiumsulfate (MgSO₄) and the solvent was removed on a rotary evaporator. Thecrude product was decolorized with charcoal and stabilized withphenothiazine (28 mg). The crude product was further purified with flashchromatography (normal phase, hexanes/EtOAc) to yield the product as anoily liquid (43.8 g, 70.8%).

Synthesis of Carbamate Crosslinker, 12: To an oven-dried three-neckround bottom flask fitted with a stir bar was added phenothiazine (0.7mg), N-(5-isocyanatopentyl)-2-methyl-2-propenamide (8, 730 mg, 4.31mmol), toluene (5 mL), and triethylamine (600 μL) to the flask. Asolution of allyl 3-(4-hydroxyphenyl)propionate (11, 740 mg, 3.59 mmol)in toluene (6 mL) was added. The solution was placed in an oil bath andrefluxed overnight. The solvent was removed at the end of the reactionto obtain the crude product, which was separated on a flash column toyield the product as a white solid (470 mg).

Example 3 Biodegradable Crosslinker

Synthesis of oxalate diester crosslinker, 15: To a 100 mL round bottomflask with a stir bar was added oxalic acid (13, 5.4 g, 60 mmol),1-butyl-3-methylimidazolium bromide ([Bmim]Br) (18 g, 84 mmol) and4-methoxyphenol (120 mg, 0.97 mmol). The content was melted at 90° C.with stirring for 15 minutes. After adding glycidyl methacrylate (14,17.04 g. 120 mmol), the reaction was stirred at 90° C. for 1 hour. Thinlayer chromatography stain with 4-(4-nitrobenzyl)pyridine showed fullconsumption of the epoxide. The reaction mixture was suspended in 200 mLof EtOAc and washed with water (100 mL×2), saturated sodium bicarbonate(100 mL×2), and brine (100 mL). The organic phase was collected anddried over sodium sulfate. The crude was dried under vacuum and purifiedwith flash chromatography (DCM/EtOAc). Total of 12.7 g of purifiedproduct was obtained as a clear liquid.

Example 4 Biodegradable Crosslinker

Synthesis of 1,3-diisocyanatopropane, 17: To a 500 mL three-neck roundbottom flask fitted with a stir bar was added toluene (109 mL) andglutaryl dichloride (16, 8.6 g, 53 mmol). The flask was then cooled inan ice bath. Then Adogen 464 (52 μL) was added. In a separate Erlenmeyerflask, sodium azide (3.62 g, 55.65 mmol) was dissolved in distilledwater (109 mL). The sodium azide solution was then added to the reactionmixture chilled on the ice bath. The reaction mixture was stirred atroom temperature for 1.5 hours and then was poured into a 500 mLseparatory funnel. The aqueous layer was drained and the toluenefraction was washed with distilled water (100 mL×1), followed bysaturated NaCl solution (100 mL×1). The organic fraction was dried overanhydrous Na₂SO₄. The organic fraction was then filtered over a Buchnerfunnel, and the filtrate was placed on a rotary evaporator until about80 grams of toluene was removed. The diisocyanate was kept as a solutionin toluene and stored in a fridge.

Synthesis of dicarbamate crosslinker, 18: A solution consisting of about35.1% (wt %) of the diisocyanatopropane, 17 in toluene was prepared asdescribed above. To a 500 mL three-neck round bottom flask fitted with astir bar, under argon was added the diisocyanatopropane solution (17,1.2 g), allyl 3-(4-hydroxyphenyl)propionate (11, 3.93 g, 19.1 mmol),toluene (54.1 mL), and triethylamine (2.44 mL, 17.49 mmol) sequentially.The reaction was placed in an oil bath and heated to reflux. After 2hours of reaction, an aliquot of the diisocyanatopropane solution (17, 1g) was added to the reaction. After 2.5 hours of reaction, anotheraliquot of the diisocyanatopropane solution (17, 1 g) was added. Thereaction was refluxed overnight. After cooling to room temperature, thereaction was washed with 5% citric acid (50 mL×1) and saturated sodiumchloride (50 mL×1). The solution was dried over anhydrous Na₂SO₄ andfiltered. The filtrate was concentrated on a rotary evaporator to affordthe product as a white solid (4.62 g).

Example 5 Biodegradable Crosslinker

Synthesis of oxalate diester crosslinker, 20: To a 1 liter three-neckround bottom flask fitted with an addition funnel and a stir bar wasadded 1-phenyl-3-buten-1-ol (19, 2 g, 13.5 mmol) and tetrahydrofuran(THF) (340 mL). To this solution was added pyridine (7 mL, 86.6 mmol).The flask was then cooled on an ice bath. To the addition funnel wasadded THF (170 mL) and oxalyl chloride (0.58 mL, 6.57 mmol). The oxalylchloride solution was added into the flask dropwise over 50 min. After40 min of stirring, more oxalyl chloride (0.58 mL, 6.75 mmol) was added.The reaction was stirred for an additional 50 min, before it was pulledout of the ice bath. To work up, the precipitate was filtered off. Thesolution was concentrated to about 30 mL. Ethyl acetate (50 mL) wasadded to the flask to dissolve the residue. The ethyl acetate solutionwas washed with 5% citric acid solution (100 mL×1) and saturated NaHCO₃solution (100 mL×1). The organic fraction was dried over MgSO₄. Thesolvent was removed on a rotary evaporator to afford the product as ayellow oil.

Example 6 Biodegradable Crosslinker

Synthesis of dicarbamate crosslinker, 23: To an oven-dried 2 Lthree-neck round bottom flask fitted with a stir bar and a refluxcondenser, under argon was added hexamethylene diisocyanate (22, 19.1mL, 0.119 mol), toluene (760 mL), and triethylamine (36.5 mL, 0.262mol). Added N-(4-hydroxyphenyl)methacrylamide (21, 50.7 g, 0.286 mol)and 25.4 mg hydroquinone to the flask. Stirred vigorously and untileverything dissolved. The flask was placed in a 110° C. oil bath orheating mantel and heated to reflux the reaction overnight. To work up,the toluene fraction was washed with 5% citric acid (200 mL×2) andsaturated NaCl solution (200 mL×1). The toluene fraction was poured intoa tared flask and the solvent was removed on a rotary evaporator. Thefraction was separated on the flash chromatography to afford the finalproduct as a white solid.

Example 7 Biodegradable Crosslinker

Synthesis of hexa(ethylene glycol) dithiol acetate, 25: To a 100 mLthree-neck round bottom flask under argon was added anhydrousN,N-dimethylformamide (50 mL), followed by addition of hexa(ethyleneglycol di-p-toluenesulfonate (24, 6 g. 10.2 mmol), potassium thioacetate(7.25 g, 63.5 mmol) and potassium iodide (0.169 g, 1.02 mmol). Thereaction was heated at 90° C. under argon for 22 hours. After thereaction was cooled down to room temperature, the crude was diluted withdichloromethane (100 mL). The resulting solution was washed with water(125 mL×5). The organic layer was dried with sodium sulfate, filteredand concentrated under vacuum. The crude was purified using flashchromatography (silica, hexane/acetone) to give 3.07 g of hexa(ethyleneglycol) dithiol acetate as a clear liquid. Yield 76%, m/z 421.1 [M+Na].

Synthesis of hexa(ethylene glycol) dithiol, 26: To a 50 mL round bottomflask was added hexa(ethylene glycol) dithiol acetate (25, 3.07 g, 7.71mmol), followed by addition of 10% hydrochloric acid (15 mL) andmethanol (15 mL). The flask was connected with a condenser and thereaction mixture was heated to reflux for 3 hours. After the reactionwas cooled down to room temperature, the crude was diluted withdichloromethane (50 mL). The solution was washed with water (50 mL×3)and then saturated sodium bicarbonate (50 mL×3). The organic layer wasdried with sodium sulfate, filtered and concentrated under vacuum. Thecrude was purified using flash chromatography (silica,dichloromethane/acetone) to give 1.50 g of hexa(ethylene glycol)dithiol. Yield 62%.

Synthesis of hexa(ethylene glycol) dithiol methacrylate, 27: To a 100 mLthree-neck round bottom flask under argon was added 50 mL of anhydrousdichloromethane followed by addition of hexa(ethylene glycol) dithiol(26, 1.50 g, 4.78 mmol). The reaction mixture was chilled on ice for 30min. To the reaction mixture was added 4-dimethylaminopyridine (0.12 g,1 mmol) and methacrylic acid (1.6 mL, 19.1 mmol). The reaction mixturewas then stirred for 15 min followed by addition of1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. The reaction wascontinued to stir for 3 hours at 0° C. until thin layer chromatographywith iodine spray indicated that the dithiol was fully consumed. Thereaction mixture was extracted with saturated sodium bicarbonate (50 mL)to remove excess methacrylic acid. The aqueous layer was extracted withethyl acetate (50 mL×2). The organic layers were combined, dried withsodium sulfate, filtered and concentrated under vacuum. The crude wasreconstituted in 50 mL of ethyl acetate/dichloromethane (3:7) and passedthrough 10 g of silica. The silica was further washed with 100 mL ofethyl acetate/dichloromethane (3:7). The washes were combined andconcentrated under vacuum. The crude was purified using flashchromatography (silica, dichloromethane/ethyl acetate) to give 1.85 g ofhexa(ethylene glycol) dithiol methacrylate as a clear liquid. Yield 86%,m/z 473.2 [M+Na], ¹H NMR (DIMETHYL SULFOXIDE-d): δ 1.915 (6H), 3.08(4H), 3.51 (16H), 3.53 (4H), 5.75 (2H), 6.035 (2H).

Example 8 Preparation of Particles

Mineral oil (300 mL) was added to a sealed jacketed-reaction vesselequipped with an overhead stirring element and a heating elementmaintained at 70° C. The vessel was sparged with argon for at least 4hours while mixing. A prepolymer solution was prepared by dissolving 1.5g dimethylacrylamide, 1.5 g glycerol monomethacrylate, 4.6 g3-sulfopropyl acrylate, 0.35 g of azobisisobutyronitrile and 5.5 g of acrosslinker prepared in Examples 1-7, in 25.0 g ofN,N-dimethylformamide. Once dissolved, the solution was sparged withargon for 5 min. Azobisisobutyronitrile (0.40 g) was added to thereaction vessel and overhead stirring increased to 300 rpm. Afterapproximately 10 min, an aliquot of SPAN® 80 (0.8 mL) was added to themineral oil and allowed to mix. The prepolymer solution was added to thereaction vessel and the resulting suspension was allowed to polymerizefor an hour before the heat was turned off. The resulting solution wasmixed in the reaction vessel overnight.

Example 9 Purification of Particles

After the polymerization was complete, an aliquot of hexane was added tothe reaction vessel and the polymer particles were washed to removeleftover mineral oil. The particles were separated from the solution,and washed with an aliquot of N,N-dimethylformamide. Washes with freshportions of solution were repeated for hexane and N,N-dimethylformamide.The resulting mixture was washed three times with phosphate bufferedsaline (PBS).

The particles were separated by sizes using a sieving process. Sieveswere stacked from the largest size (on top) to the smallest size (onbottom). A sieve shaker was utilized to aid in the sieving process. Theparticles were placed on the top sieve along with an aliquot of PBS.Once all the particles had been sorted, they were collected and placedin bottles according to their size.

After sieving, the particles were dehydrated to extend their shelf life.While mixing, the particles were placed in a graded series ofacetone/water mixtures. For at least 24 hours, the particles weresuspended in solvent mixtures ranging from 75% to 100% acetone.Subsequently, the particles were lyophilized, packaged, and sterilized.

Example 10 Degradation of Particles

Samples of particles prepared with differing monomers, crosslinkers andreagent concentrations were placed in PBS and stored at 37° C. todetermine degradation time. The visual analysis included color andtransparency of the particles, ability to see the particle outline, andthe number of particles visible. The grading scale for the samplesincluded (5) no change in particle numbers, outlines, or quantity fromthe beginning of the experiment, (3) faint particle outline with a goodnumber of particles still visible, (1) very few particles visible, and(0) no particles observed in sample. Results for the comparison ofdifferent crosslinking agents are illustrated in FIG. 1. The resultsillustrate that degradation rate can be dependent on the structure ofthe crosslinker used.

FIG. 2 graphically shows degradation time at 37° C. as a function of twodifferent types of monomers with the same crosslinker and concentration.As illustrated, degradation can be dependent on the type of monomersused. Selection of the monomer(s) and crosslinker(s) used are twoproperties that can be varied to tailor degradation time as needed.

FIG. 3 graphically shows degradation time at 37° C. as a function of theamount of crosslinker. As illustrated, the greater the percentage ofcrosslinker the slower the degradation rate. This feature can also bevaried to tailor degradation time as needed.

Example 11 In Vitro Elution of Pharmaceutical Agents from Particles

For in vitro elution testing, drug was loaded on 1 mL samples ofmicrospheres of approximately 400±100 micron diameter. Microspherealiquots were loaded with 37.5 mg of doxorubicin in water or 50 mg ofirinotecan in citrate buffer. Samples were incubated for 18 hours. Drugwas eluted from the samples in a Sotax USP 4 dissolution apparatus.Samples were taken at incremental time intervals and analyzed by highperformance liquid chromatography. Peak area was recorded (FIG. 4).Percent and concentration of drug eluted were calculated for each timeinterval. A 1 mL microsphere sample loaded with 37.5 mg doxorubicineluted 24.5 mg (65%) over the first day; and, a sample loaded with 50 mgirinotecan eluted over 45 mg (95%) over the first day.

Example 12 In Vivo Elution of Pharmaceutical Agents from Particles

Blood samples were obtained to determine the systemic concentration ofpharmaceutical agent before embolization as well as 20, 40, 60, 120 and180 minutes post-embolization. Plasma was prepared by centrifugation andthe samples were frozen at −80° C. until analysis. Quantitation was donevia liquid chromatography-tandem mass spectrometry (LC/MS/MS) using anAgilent 1260 Infinity HPLC system coupled with ABSciex 4000 Q TrapLC/MS/MS system. Chromatographic separation was performed using anAgilent Poroshell 120 C18 column (4.6 mm×50 mm, 2.7 μm) at 25° C. andmobile phases consisting of A: 0.1% formic acid in acetonitrile and B:0.1% formic acid in water. The plasma samples were precipitated with 3fold excess (v/v) of acetonitrile containing 50 ppb of an internalstandard. After being vortexed and centrifuged at 13,000 rpm at 4° C.for 10 minutes, the supernatant of each sample was diluted with 0.1%formic acid in water. Injection of 20 μL of the diluted sample wasperformed. The calibration curve was prepared by spiking blank plasmaover the analytical range for each agent. The systemic concentration ofeach agent in plasma overtime is shown in FIGS. 5 and 6.

Example 13 Preparation of Particles

Mineral oil (500 mL) was added to a sealed jacketed-reaction vesselequipped with an overhead stirring element and a heating elementmaintained at 74° C. The vessel was sparged with argon for at least 4hours while mixing. A prepolymer solution was prepared by dissolving 0.5g dimethylacrylamide, 2.75 g glycerol monomethacrylate, 4.9 g3-sulfopropyl acrylate, 0.35 g of azobisisobutyronitrile and 5.25 g of acrosslinker prepared in Examples 1-7, in 25.0 g of dimethyl sulfoxide.Once dissolved, the solution was sparged with argon for 5 min. Ifdesired, an aliquot of Triton® X-100 (0.2 mL) can be added to theformulation and allowed to mix. Azobisisobutyronitrile (0.50 g) wasadded to the reaction vessel and overhead stirring increased to 325 rpm.After approximately 2 min, an aliquot of SPAN® 80 (2.5 mL) was added tothe mineral oil and allowed to mix. The prepolymer solution was added tothe reaction vessel and the resulting suspension was allowed topolymerize for an hour before the heat was turned off. The resultingsolution was mixed in the reaction vessel overnight.

Example 14 Washing of Particles

After the polymerization was complete, an aliquot of hexane was added tothe reaction vessel and the polymer particles were washed to removeleftover mineral oil. The particles were separated from the solution,and washes with fresh portions of solution were repeated. The particleswere once again separated from solution, and washed with an aliquot ofisopropyl alcohol. After decanting off the solution, the particles werewashed with a mixture of isopropyl alcohol and phosphate buffered saline(PBS). The resulting mixture was washed three times with 70% isopropylalcohol.

The particles were separated by sizes using a sieving process. Sieveswere stacked from the largest size (on top) to the smallest size (onbottom). A sieve shaker was utilized to aid in the sieving process. Theparticles were placed on the top sieve along with an aliquot of 70%isopropyl alcohol. Once all the particles had been sorted, they werecollected and placed in bottles according to their size.

After sieving, the particles were dehydrated to extend their shelf life.While mixing, the particles were placed in a graded series ofacetone/water mixtures. For at least 24 hours, the particles weresuspended in solvent mixtures ranging from 75% to 100% acetone.Subsequently, the particles were lyophilized, packaged, and sterilized.

The preceding disclosures are illustrative embodiments. It should beappreciated by those of skill in the art that the devices, techniquesand methods disclosed herein elucidate representative embodiments thatfunction well in the practice of the present disclosure. However, thoseof skill in the art should, in light of the present disclosure,appreciate that many changes can be made in the specific embodimentsthat are disclosed and still obtain a like or similar result withoutdeparting from the spirit and scope of the invention.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.” Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe following specification and attached claims are approximations thatmay vary depending upon the desired properties sought to be obtained bythe present invention. At the very least, and not as an attempt to limitthe application of the doctrine of equivalents to the scope of theclaims, each numerical parameter should at least be construed in lightof the number of reported significant digits and by applying ordinaryrounding techniques. Notwithstanding that the numerical ranges andparameters setting forth the broad scope of the invention areapproximations, the numerical values set forth in the specific examplesare reported as precisely as possible. Any numerical value, however,inherently contains certain errors necessarily resulting from thestandard deviation found in their respective testing measurements.

The terms “a” and “an” and “the” and similar referents used in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Recitation of ranges of values herein is merely intended toserve as a shorthand method of referring individually to each separatevalue falling within the range. Unless otherwise indicated herein, eachindividual value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g. “such as”) provided herein isintended merely to better illuminate the invention and does not pose alimitation on the scope of the invention otherwise claimed. No languagein the specification should be construed as indicating any non-claimedelement essential to the practice of the invention.

The use of the term “or” in the claims is used to mean “and/or” unlessexplicitly indicated to refer to alternatives only or the alternativesare mutually exclusive, although the disclosure supports a definitionthat refers to only alternatives and “and/or.”

Groupings of alternative elements or embodiments of the inventiondisclosed herein are not to be construed as limitations. Each groupmember may be referred to and claimed individually or in any combinationwith other members of the group or other elements found herein. It isanticipated that one or more members of a group may be included in, ordeleted from, a group for reasons of convenience and/or patentability.When any such inclusion or deletion occurs, the specification is hereindeemed to contain the group as modified thus fulfilling the writtendescription of all Markush groups used in the appended claims.

Embodiments of this invention are described herein, including the bestmode known to the inventors for carrying out the invention. Of course,variations on those embodiments will become apparent to those ofordinary skill in the art upon reading the foregoing description. Theinventor expects those of ordinary skill in the art to employ suchvariations as appropriate, and the inventors intend for the invention tobe practiced otherwise than specifically described herein. Accordingly,this invention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

Specific embodiments disclosed herein may be further limited in theclaims using consisting of or consisting essentially of language. Whenused in the claims, whether as filed or added per amendment, thetransition term “consisting of” excludes any element, step, oringredient not specified in the claims. The transition term “consistingessentially of” limits the scope of a claim to the specified materialsor steps and those that do not materially affect the basic and novelcharacteristic(s). Embodiments of the invention so claimed areinherently or expressly described and enabled herein.

Further, it is to be understood that the embodiments of the inventiondisclosed herein are illustrative of the principles of the presentinvention. Other modifications that may be employed are within the scopeof the invention. Thus, by way of example, but not of limitation,alternative configurations of the present invention may be utilized inaccordance with the teachings herein. Accordingly, the present inventionis not limited to that precisely as shown and described.

We claim:
 1. An embolic system including: a syringe, a vial, or acombination thereof; and polymer particles comprising at least onemonomer including at least one functional group and at least onecrosslinker having a structure


2. The embolic system of claim 1, wherein the polymer particles have adiameter between about 40 μm and about 1,200 μm.
 3. The embolic systemof claim 1, wherein the polymer particles have a diameter between about75 μm and about 1,200 μm.
 4. The embolic system of claim 1, wherein theat least one functional group is acrylate, acrylamide, methacrylate, ormethacrylamide.
 5. The embolic system of claim 1, wherein the at leastone monomer includes an ionizable functional group.
 6. The embolicsystem of claim 5, wherein the ionizable functional group is basic. 7.The embolic system of claim 5, wherein the ionizable functional group isacidic.
 8. The embolic system of claim 1, wherein the polymer particlesinclude a second crosslinker including a second linkage selected from anester, a thioester, a carbonate, a peptide cleavable by matrixmetalloproteinases, a peptide cleavable by matrix collagenases, apeptide cleavable by matrix elastases, and a peptide cleavable by matrixcathepsins.
 9. The embolic system of claim 1, wherein the polymerparticles are biodegradable.
 10. The embolic system of claim 1, whereinthe polymer particles are substantially degraded within about 1 monthsof implantation.
 11. The embolic system of claim 1, wherein the at leastone monomer is dimethylacrylamide.
 12. The embolic system of claim 1,wherein the at least one monomer is acrylamide.
 13. A method oftreatment, the method comprising: delivering a solution includingpolymer particles through a delivery device to a treatment site, whereinthe polymer particles include at least one monomer including at leastone functional group and at least one crosslinker having a structure


14. The method of claim 13, wherein the polymer particles have adiameter between about 40 μm and about 1,200 μm.
 15. The method of claim13, further comprising: mixing a radiopaque contrast agent with thepolymer particles.
 16. The method of claim 13, wherein the delivering isthrough a catheter, a microcatheter, or a needle.
 17. The method ofclaim 13, further comprising: occluding blood flow using the polymerparticles.
 18. The method of claim 13, wherein the polymer particlesinclude a second crosslinker including a second linkage selected from anester, a thioester, a carbonate, a peptide cleavable by matrixmetalloproteinases, a peptide cleavable by matrix collagenases, apeptide cleavable by matrix elastases, and a peptide cleavable by matrixcathepsins.
 19. The method of claim 13, wherein the polymer particlesare biodegradable.
 20. The method of claim 19, wherein the polymerparticles are substantially degraded within about 6 months ofimplantation.